Multi server installation across private (RFC 1918) and official networks

Hello,

I want to set up a ZCS 7.1.3 network edition system with four servers. Two of the servers, the central directory server for ZCS and other applications and the mailstore server, should be in a private network with private RFC 1918 IP addresses and a DNS server for the private network. The other two servers, one MTA handling incoming and outgoing emails and one proxy server for web and IMAP proxying, should have official IP addresses with worldwide resolvable names. Between the two networks there is a packet filtering firewall with two interfaces which NATs the internal network. All in all I have:

should be no problem at all. we are running a similar setup with 2 balanced frontends, 3 backends and 1 ldap master. 3 backends and the ldapmaster do have private addresses. you should look if the frontends can reach the backends with all needed ports (route lookup, proxy ports)

I was quite sure that it should be possible although Zimbra support told me that it I want to achieve an unsupported setup.
Can you please tell me what you configured during install? That's what I did.